Modular control system and method for water heaters

ABSTRACT

A water heating system includes a tank, one or more heating elements mounted on the water heating system, and a first controller mounted on the tank. The first controller is coupled to the one or more heating elements and includes logic to activate and deactivate the heating elements according to a first threshold value. The water heater also includes a second controller that is selectively coupled to the first controller and configured to communicate the first threshold value to the first controller, and perform an additional function related to the operation of the water heater. The first controller is configured to receive the first threshold value from the second controller and control the one or more heating elements based on the received threshold value, and to control the one or more heating elements mounted on the water heating system in a physical absence of the second controller.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/692,182 entitled “Modular Control System AndMethod for Water Heaters” filed Mar. 27, 2007, which is incorporatedherein by reference, and which is a continuation-in-part of and claimspriority to U.S. patent application Ser. No. 11/201,665 entitled“Modular Control System And Method for Water Heaters” filed Aug. 11,2005, and issued as U.S. Pat. No. 7,613,855, which is also incorporatedherein by reference. The U.S. patent application Ser. No. 11/201,665claims priority to U.S. Provisional Patent Application No. 60/604,689filed Aug. 26, 2004, also incorporated herein by reference. The U.S.patent application Ser. No. 11/692,182 also claims priority to U.S.Provisional Application No. 60/908,132, entitled “Water Heating Systemsand Methods” filed Mar. 26, 2007, and also incorporated herein byreference.

RELATED ART

Water heaters are often employed to provide users with heated water,which is drawn from a water tank and usually dispensed from a faucet,showerhead, or like device. During operation, a water heater tanknormally receives unheated water from a water source, such as a waterpipe. The tank includes a controller having a user interface that allowsa user to set a desired temperature for the water being held by thetank. If the tank's water temperature falls below a lower temperaturethreshold, then the controller activates a heating element for warmingthe tank's water. When activated, the heating element begins to heat thewater within the tank, and the heating element continues to heat thewater until the water's temperature reaches or exceeds an uppertemperature threshold.

Controllers for conventional water heaters are becoming increasinglysophisticated using more complicated algorithms for controlling heatingelements and providing additional features, such as detection of dryfire conditions and other conditions pertinent to the operation of thewater heater. Moreover, for different models of water heaters,manufacturers often install different controllers that provide differentfeatures. For example, for a standard water heater, a manufacturer mayinstall a basic controller for providing basic functionality, such as asimple algorithm for controlling heating elements. However, for ahigher-end water heater, the manufacturer may install a moresophisticated controller for providing additional features and/or betterperformance. Such a higher-end water heater can usually be sold at ahigher price relative to lower-end or other standard water heaters.

A water heater manufacturer may have different assembly lines fordifferent models of water heaters. Unfortunately, adding more assemblylines to accommodate different water heater models can significantlyincrease manufacturing costs since many assembly lines must be tooledwith equipment separate from other assembly lines. Further, it ispossible to retrofit one model of a water heater with a differentcontroller after manufacturing in order to upgrade the water heater. Inparticular, depending on the configuration of the water heater,including the design of the current controller and the new controller,it is possible to remove the current controller and to replace it with anew controller that provides better functionality and/or more features.However, such retrofitting can be burdensome and problematic.

In addition, it is not always possible to replace a current controllerwith a new controller without damaging or significantly reconfiguringother portions of the water heater, such as the water tank and/orconnections leading to the heating elements. Further, ensuring areliable connection between the new controller and the heating elementscan be particularly problematic, and retrofitting in general can beproblematic if it is being performed by a consumer or unskilledtechnician who is unfamiliar with the design of the water heater.

Thus, better techniques for providing different models of water heatersat lower costs are generally desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be better understood with reference to the followingdrawings. The elements of the drawings are not necessarily to scalerelative to each other, emphasis instead being placed upon clearlyillustrating the principles of the disclosure. Furthermore, likereference numerals designate corresponding parts throughout the severalviews.

FIG. 1 is a block diagram illustrating an exemplary water heater inaccordance with the present disclosure.

FIG. 2 is a block diagram illustrating an exemplary first controller forthe water heater depicted in FIG. 1.

FIG. 3 is a block diagram illustrating the controller of FIG. 2.

FIG. 4 is a block diagram illustrating an exemplary second controllerinterfaced with the first controller of FIG. 2.

FIG. 5 is a block diagram illustrating the second controller of FIG. 4.

FIG. 6 is a flow chart illustrating an exemplary use of the water heaterdepicted in FIG. 1.

FIG. 7 is a three-dimensional perspective of an exemplary housing thatmay be used to house a controller, such as is depicted in FIG. 5.

FIG. 8 is a top view of the housing depicted in FIG. 7.

FIG. 9 is a back view of the housing depicted in FIG. 7.

FIG. 10 is a side view of an exemplary water heater tank on which acontroller, such as is depicted in FIG. 3, is mounted.

FIG. 11 is a side view of the water heater tank of FIG. 10 after thehousing of the FIG. 7 has been mounted on the tank.

DETAILED DESCRIPTION

The present disclosure generally relates to systems and methods forenabling modular control of water heaters such that different models ofwater heaters can be efficiently provided. In this regard, a firstcontrol module is used to provide a first set of functionality and/orfeatures for a water heater. If desired, a second control module canthen be added to provide a second set of functionality and/or featuresfor the water heater. Thus, the second control module, when added,essentially upgrades the water heater to make it more attractive toconsumers that are willing to pay a higher price or fee for the secondset of functionality and/or features enabled by the second controlmodule. Moreover, enabling the water heater to be upgraded withoutremoving the first control module can facilitate the upgrading processparticularly for users who are unfamiliar with the design of the waterheater.

FIG. 1 depicts a water heater 10 comprising a tank 15 filled, at leastpartially, with water. In the embodiment shown by FIG. 1, the tank 15 isresting on a stand 17, although such a stand 17 is unnecessary in otherembodiments. The water within the tank 15 can be heated by one or moreheating elements 19 submerged within the water. Based on informationfrom a temperature sensor 21, such as a thermistor, mounted on the tank15, the operation of the heating element 19 is controlled by a controlsystem 20, which is also mounted on the tank 15. It should be noted,however, that mounting of the control system 20 and/or temperaturesensor 21 on the tank 15 is unnecessary, and the control system 20and/or temperature sensor 21 may be positioned differently in otherembodiments. Exemplary techniques for controlling the heating element 19is described in U.S. patent application Ser. No. 10/772,032, entitled“System and Method for Controlling Temperature of a Liquid Residingwithin a Tank,” and filed on Feb. 4, 2004, which is incorporated hereinby reference.

As shown by FIG. 2, the control system 20 comprises a controller 27having control logic 25. A communication port 29 enables devicesexternal to the controller 27 to communicate with the control logic 25.In one embodiment, the communication port 29 comprises a universalsynchronous/asynchronous receive/transmit (USART) interface, such as forexample, a serial RS232 interface, although other type of ports may beused in other embodiments. Indeed, in at least some other embodiments,the communication port 29 may enable wireless communication to allow thelogic 25 to communicate with external devices via wireless signals. Asan example, the communication port 29 may comprise an infraredtransmitter and/or an infrared receiver, although other types ofwireless transmitters and/or receivers may be used in other embodiments.The components of the controller 27 may be housed by one or more housingunits (not specifically shown).

A user output device 33, such as for example one or more light emittingdiodes (LEDs), a liquid crystal display (LCD) or other types of outputdevices, may be used to output data to a user. Further, a user inputdevice 35, such as buttons or a keypad, for example, may be used toinput data from a user. As shown by FIG. 2, the control logic 25,communication port 29, user output device 33, and user input device 35may be integrally mounted on a base 36 so that the controller 47 forms aunitary structure.

The control logic 25 may be implemented in hardware, software, or acombination thereof. In an exemplary embodiment illustrated in FIG. 3,the control logic 25, along with its associated methodology, isimplemented in software and stored in memory 39.

Note that the control logic 25, when implemented in software, can bestored and transported on any computer-readable medium for use by or inconnection with an instruction execution system or device, such as acomputer-based system, processor-containing system, or other system ordevice that can fetch and execute instructions. In the context of thisdocument, a “computer-readable medium” can be any means that cancontain, store, communicate, propagate, or transport a program for useby or in connection with an instruction execution system or device. Thecomputer readable-medium can be, for example but not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor device or propagation medium.

The exemplary embodiment of the controller 27 depicted by FIG. 3comprises at least one conventional processing element 37, such as adigital signal processor (DSP) or a central processing unit (CPU), thatcommunicates to and drives the other elements within the controller 27via a local interface 38, which can include at least one bus. Indeed,when the control logic 25 is implemented in software, the processingelement 37 can fetch and execute instructions from the control logic 25to implement the functionality of the control logic 25, as is describedherein.

The control logic 25 is configured to control the operation of theheating element 19 (FIG. 1) in accordance with at least one algorithm.As an example, the control logic 25 may receive inputs from thetemperature sensor 21 to determine a temperature of the water within thetank 15. The control logic 25 may then activate the heating element 19when the temperature falls below a first specified threshold anddeactivate the heating element 19 when the temperature rises above asecond specified threshold. Other techniques for controlling the heatingelement 19 are disclosed in U.S. patent application Ser. No. 10/772,032,as well as U.S. Provisional Application No. 60/579,757, entitled “Systemand Method for Detecting Failure of a Relay-Based Circuit,” and U.S.Provisional Application No. 60/584,401, entitled “Apparatus and Methodfor Fluid Temperature Control,” which are all incorporated herein byreference. As indicated by these other applications, the logic 25 may beconfigured to perform other functionality, such as for example, testingfor dry fire conditions, adaptively adjusting a hysteresis of theheating element 19, and performing diagnostic functions, such asdetecting a failure or imminent failure of the heating element 19. Inaddition, the controller 27 may be configured in accordance with U.S.patent application Ser. No. 11/692,117, entitled “Water Hearing Systemsand Methods,” and filed on Mar. 27, 2007, which is incorporated hereinby reference.

In one embodiment, control logic 45 of a second controller 47 may beinterfaced with the control logic 25, as shown by FIG. 4. Such controllogic 45 may be housed within one or more housing units separate fromthe housing unit or units of the control logic 25.

In the embodiment shown by FIG. 4, the controller 47 comprises acommunication port 49 that is coupled to the communication port 29 ofcontroller 27 by a conductive connection 52. Thus, the control logic 45of controller 47 is able to communicate with the control logic 25 ofcontroller 27 via the conductive connection 52 and communication ports29 and 49. The controller 47 may be mounted on the tank 15 and/or thecontroller 27. Alternatively, the controller 47 may be located remotelyfrom the tank 15. In such an embodiment, the connection 52 may extendfrom the port 29 to the port 49, or wireless signals may be communicatedbetween the ports 29 and 49.

The control logic 45 is configured to control the operation of theheating element 19 and/or provide other functions, such as thosedescribed in the aforementioned patent applications. Further, thecontrol logic 45 may be implemented in hardware, software, or acombination thereof. In an exemplary embodiment illustrated in FIG. 5,the control logic 45, along with its associated methodology, isimplemented in software and stored in memory 59.

Note that the control logic 45, when implemented in software, can bestored and transported on any computer-readable medium for use by or inconnection with an instruction execution system or device, such as acomputer-based system, processor-containing system, or other system ordevice that can fetch and execute instructions. In addition, theexemplary embodiment of the controller 47 depicted by FIG. 5 comprisesat least one conventional processing element 57, such as a digitalsignal processor (DSP) or a central processing unit (CPU), thatcommunicates to and drives the other elements within the controller 47via a local interface 58, which can include at least one bus. Indeed,when the control logic 45 is implemented in software, the processingelement 57 can fetch and execute instructions from the control logic 45to implement the functionality of the control logic 45, as is describedherein.

The control logic 45 may control components, such as heating elements,directly or may exercise such control in conjunction with the controllogic 25. As an example, the control logic 25 may be configured tocontrol the operation of the heating element 19 according to aparticular algorithm, such as one of the algorithms described in theaforementioned patent applications. The control logic 45, on the otherhand, may be configured to control the operation of the heating element19 according to a different algorithm, such as another algorithmdescribed in the aforementioned patent applications. Thus, the controlof the water heater 10 is modular in that separate logic 25 and/or 45may be selectively used separately or in conjunction with one another tocontrol one or more functions of the water heater 10.

As with the control logic 25, the control logic 45 of controller 47 maybe used to control various functions in addition to or in lieu ofoperational control of heating elements, such as for example, testingfor dry fire conditions, adaptively adjusting a hysteresis of a heatingelement, and performing diagnostic functions, such as detecting afailure or imminent failure of a heating element. A user output device63, such as an LED or LCD, for example, may be used by the control logic45 to output information to a user. Further, a user input device 65,such as buttons or a keypad, for example, may be used to input data froma user. As shown by FIG. 4, the control logic 45, communication port 49,user output device 63, and user input device 65 may be integrallymounted on a base 56 so that the controller 47 forms a unitarystructure.

In one embodiment, the operation of the heating element 19 is controlledby one of the control logic 25 or 45 depending on the desiredconfiguration of the water heater 10. For example, if the controller 47is not interfaced with the controller 27 or is not operational, then thecontrol logic 25 may control the operation of the heating element 19according to a first algorithm. Otherwise, the control logic 45 maycontrol the operation of the heating element 19 according to a secondalgorithm.

The modular approach to controlling the water heater 10 may be used toefficiently provide users with different feature operations. Forexample, a manufacturer of water heaters 10 could manufacture a largenumber of water heaters having the controller 27 and not the controller47. The controller 27 could provide a basic set of functionality, suchas simple algorithms for controlling the heating element 19. Further,the output device 33 could comprise low cost components, such as LEDs.If, however, a user of a particular one of the manufactured waterheaters 10 desires a higher-end type of water heater, then thecontroller 47 could be introduced to provide additional and/or betterfeatures.

For example, the control logic 45 could utilize one or more betteralgorithms for controlling the heating element 19. As a further example,the control logic 45 could utilize an algorithm that tracks a usagehistory of the water tank or heating element 19 and efficiently controlthe heating element 19 based on this history as described by U.S. patentapplication Ser. No. 10/772,032. Also, the output device 63 may providebetter components as compared to output device 33. For example, asophisticated LCD screen may be used to provide output for the device 63whereas LEDs may be used to provide output for the device 33. As anexample, a screen of the device 63 may convey textual messages, and if aheating element failure or other event is detected, the screen of device63 may provide a message explaining the event that has been detected.Such a screen may also provide information about the thresholds, alsoreferred to as “set points,” that are used to control the heatingelement 19, as well as information about the detected water temperature.The output device 63 may also be configured to provide audibleindications, such as beeps or pre-recorded messages, that the outputdevice 33 may be incapable of providing.

Moreover, by installing or otherwise introducing the controller 47, thewater heater 10 can essentially be upgraded to a more desirable model.Thus, a manufacturer or retailer is able to efficiently upgrade thewater heater 10 to a more desirable or expensive model by merelyproviding the controller 47 to the customer that is purchasing the waterheater 10. Further, different models of the controller 47 may beavailable such that a user can easily select a particular set offeatures to which he would like to upgrade.

In addition, a manufacturer may elect to use low cost components for thecontroller 27. For example, if the control logic 25 and 45 areimplemented in software, then a low cost processing element 37 may beselected for executing the instructions of the logic 25. However, thelogic 45 may be configured to utilize a more sophisticated algorithmthat requires more processing power or speed than that provided by theprocessing element 37 selected for controller 27. Thus, a more expensiveprocessing element 57 may be selected for the controller 47.

Moreover, the manufacturer can use low cost components to initiallymanufacture the water heater 10, and the manufacturer or retailer couldbear the cost of the higher cost or additional components of thecontroller 47 only for the upgraded units, which would likely command ahigher purchase price or an additional fee after the initial purchase.Thus, for units that are not to be sold with the controller 47, it isunnecessary for the manufacturer to utilize higher cost components thatare not needed for operation of this controller 47. Such a feature couldhelp to reduce the cost of the non-upgraded water heaters, inparticular, since it is unnecessary for such components to fully supportthe functionality provided by the controller 47. In this regard,components for supporting the functionality of the controller 47 may bewithin the controller 47 and interfaced with the controller 27 at thetime of the upgrade. Thus, the non-upgraded water heaters 10 are able tohave a relatively low cost structure yet have the capability of easilyand efficiently upgrading to higher performance.

An exemplary use of a water heater 10 in accordance with an embodimentof the present disclosure will be described hereafter.

For illustrative purposes, assume that the control logic 25 isconfigured to control the heating element 19 in accordance with a firstalgorithm, referred to hereafter as the “user-specified thresholdalgorithm.” In this regard, the control logic 25 is configured toestablish an upper threshold and a lower threshold based on user inputsspecifying such thresholds. If the control logic 25 determines thatwater within the tank 15 falls below the lower threshold, the controllogic 25 activates the heating element 19 such that it begins to heatwater within the tank 15. If the control logic 25 determines that waterwithin the tank 15 rises above the upper threshold, the control logic 25deactivates the heating element 19 such that it is prevented fromheating water within the tank 15 until the element 19 is lateractivated. Such a user-specified threshold algorithm has been used tocontrol many conventional water heaters.

For illustrative purposes, also assume that the control logic 45 isconfigured to control the heating element 19 based on a secondalgorithm, referred to herein as the “usage history algorithm.” In thisregard, the control logic 45 is configured to activate and deactivatethe heating element 19 based on whether water temperature within thetank 15 exceeds upper and lower thresholds, as described above for theuser-specified threshold algorithm. However, the control logic 45 isconfigured to automatically track usage of the heating element 19 overtime and to automatically select the upper and lower thresholds based onthe heating element's usage history. Exemplary techniques for trackingusage of the heating element 19 and for selecting thresholds based onthe tracked usage are described in more detail in U.S. patentapplication Ser. No. 10/772,032 and other applications previouslyreferenced herein. Note that the user-specified threshold algorithm andthe usage history algorithm are described herein for illustrativepurposes, and the control logic 25 and 45 may be configured to employother algorithms in other embodiments.

For illustrative purposes, also assume that the control logic 25 isconfigured to detect a dry fire condition, which is a condition thatexists when the heating element 19 is activated without being submergedin water. Exemplary techniques for detecting a dry fire condition aredescribed in more detail in U.S. patent application Ser. No. 11/117,069,entitled “Water Heating System and Method for Detecting a Dry FireCondition for a Heating Element,” and filed on Apr. 28, 2005, which isincorporated herein by reference.

Further assume that the user output device 33 comprises an LED (notspecifically shown), referred to hereafter as the “dry fire LED,” whichis illuminated by the control logic 25 upon detection of a dry firecondition. Thus, illumination of the dry fire LED indicates that a dryfire condition has been detected. In other examples, the foregoing LEDmay be used to indicate the occurrences of other events.

In addition, assume that the user output device 63 comprises an LCD fordisplaying textual messages. It should be noted that the foregoingassumptions are made so that an exemplary operation and use of the waterheater 10 can be presented. None of the foregoing assumptions areessential to the present disclosure and may be changed for otherexamples.

Initially, the water heater system 10 is manufactured or otherwiseprovided with the controller 27 mounted on the tank 15, as shown byblock 81 of FIG. 6. Notably, controller 47 is absent from the waterheater 10 and, therefore, may not be used to control the heating element19 or provide other features with the water heater 10 until thecontroller 47 is later added, as will be described in more detailhereafter.

Assume that a consumer purchases the water heater 10 and decides to notpurchase or add the controller 47. Thus, the consumer begins to use thewater heater 10 without the controller 47, as indicated by blocks 82 and83 of FIG. 6. In such an example, the control logic 25 controls theheating element 19 in accordance with the user-specified thresholdalgorithm. Further, the control logic 25 checks for dry fire conditionsand illuminates the dry fire LED of user output device 33 if such acondition is detected. Of course, for such an illumination to be useful,the consumer or other user of the water heater 10 must be aware thatillumination of the dry fire LED indicates an occurrence of a dry firecondition.

At some point, the consumer may desire to upgrade the water heater 10.Thus, the consumer may purchase or otherwise obtain the controller 47and interface it with the controller 27, as shown by blocks 82 and 88 ofFIG. 6. In one embodiment, the foregoing is accomplished by mounting thecontroller 47 on the controller 27 such that the communication port 49is detachably coupled to the communication port 29. However, othertechniques may be used in other embodiments to interface the controllers27 and 47. For example, it is possible for the interfacing to be done byplacing the controller 47 in close proximity with the controller 27 suchthat wireless signals can be communicated therebetween.

Once the controllers 27 and 47 are interfaced, the control logic 45begins monitoring the heating element 19 to define a usage history ofthe element 19. Various techniques may be employed to monitor the usageof the heating element 19. For example, when the controllers 27 and 47are interfaced, the control logic 25 may be configured to notify thecontrol logic 45 each time the heating element 19 is activated ordeactivated. Based on these notifications, the control logic 45 candefine the heating element's usage history.

Based on the usage history, the control logic 45 determines upper andlower thresholds and begins controlling the heating element 19 accordingto the usage history algorithm. In this regard, when the control logic45 is ready to start controlling the heating element 19 via the usagehistory algorithm, the control logic 45 communicates, to the controllogic 25, a command to disable the control logic 25 from continuing tocontrol the heating element 19 according to the user-specified thresholdalgorithm. Then, the control logic 45 begins controlling the heatingelement 19 via the usage history algorithm. There are variousmethodologies that may be used to control the heating element 19according to the usage history algorithm.

For example, the control logic 45 may determine when to activate anddeactivate the heating element 19 and instruct the control logic 25 toactivate and deactivate the heating element 19 accordingly. To enablesuch a determination, the control logic 25 may periodically communicatetemperature information from the temperature sensor 21 to the controllogic 45. In other embodiments, the communication port 49 may be coupleddirectly to the connections leading to the heating element 19 and/or thetemperature sensor 21, and the control logic 45 may be configured tocontrol the heating element 19 directly without the use of control logic25. In yet another embodiment, the control logic 45 may communicate theappropriate upper and lower thresholds to the control logic 25. Thecontrol logic 25 may then control the heating element 19 using thesethresholds instead of the user defined thresholds previously employed bythe control logic 25. In such an embodiment, both the control logic 45and the control logic 25 jointly control the heating element 18accordingly to the usage history algorithm. Various other techniques maybe employed to enable the control logic 45 to control the heatingelement 19 according to the usage history algorithm.

If a dry fire condition occurs once the controller 47 is interfaced withthe controller 27, the control logic 25 preferably notifies the controllogic 45 of the detected dry fire condition. The control logic 45 thendisplays a textual message via the LCD of the user output device 63. Thetextual message may indicate that a dry fire condition has been detectedand possibly provide general information about dry fire conditions sothat the user can be more informed about the detected problem. Notethat, if desired, the control logic 25 may be configured to illuminatethe dry fire LED of the user output device 33 even after the controller47 is interfaced with the controller 27.

Although the control logic 25 is described above as detecting possibledry fire conditions after the controllers 27 and 47 are interfaced, sucha feature is unnecessary. For example, the communication port 49 may becoupled directly to the connections leading to the temperature sensor 21and the heating element 19. In such an embodiment, operation of thecontrol logic 25 may be disabled such that the control logic 25 nolonger operates as long as the controllers 27 and 47 are interfaced oras long as the control logic 45 is actively disabling the control logic25. Indeed, the control logic 45 may receive temperature informationfrom the temperature sensor 21 and detect dry fire conditions and/orother conditions without any use of the control logic 25. Further, thecontrol logic 45 may control the activation state of the heating element19 without any use of the control logic 25. Moreover, components of orassociated with the control logic 25, such as the processing element 37,may be powered down while the control logic 25 is disabled.

It should be noted that controller 27 is described above as using adifferent algorithm for controlling the heating element 19 relative tothe controller 47. Such a feature is unnecessary. For example, it ispossible for controllers 27 and 47 to use the same algorithm or for thecontroller 27 to continue controlling the heating element 19 via thesame algorithm after the controllers 27 and 47 are interfaced. In suchembodiments, the controller 47 may be different than controller 27 inother ways, such as by employing different user output components orproviding functions that are not provided by the controller 27.

FIG. 7 illustrates an exemplary housing 404 for the additionalcontroller 47. Components of the controller 47 may be housed within andprotected by the housing 404. As shown by FIG. 7, a display 411, such asa liquid crystal display, is coupled to the housing 404 so that a usercan see information displayed by the controller 47. Further, one or morebuttons 419 allows a user to submit inputs to the controller 47,although other types of user interfaces may be employed in otherembodiments.

As shown by FIGS. 7-9, the exemplary housing 404 has an exterior cover421 and an interior rim 422. The exterior cover 421, as shown by FIG. 8,has a radius of curvature consistent with that of the tank 53 so thatthe cover 421 can fit flush with the wall of the tank 53 when thecontroller 47 is mounted on the tank 53. Moreover, most conventionaltanks have a rectangular shaped compartment, in which the water heatercontroller and the base of a heating element can reside. The rim 422 ispreferably shaped so that it fits within the compartment and theexterior wall of the rim 422 contacts the wall of the compartment and isflush with the wall of the compartment along a perimeter of thecompartment. In such an example, the housing 404, along with thecontroller 47, which is housed by the housing 404, can cover thecontroller 52. Various other configurations of the housing 404 arepossible in other embodiments.

FIG. 10 shows an exemplary tank 502 of a water heating system, such asis described in U.S. patent application Ser. No. 11/692,117. The tank502 has a compartment 511 in which the controller 27 may reside. In thisregard, the controller 27 is mounted on a bracket 515 through which abase 517 of a heating element passes. The bracket 515 can be any knownor future-developed bracket for holding water heater controllers. Anexemplary bracket 517 is described in U.S. patent application Ser. No.11/692,117.

As shown by FIG. 10, a temperature sensor holding apparatus 533 alsoresides in the compartment 511. The apparatus 553 is mounted on abracket 537 through which a base 539 of another heating element passes.The bracket 537 may be similar or identical to the bracket 515. Anexemplary temperature sensor holding apparatus 533 is described in U.S.patent application Ser. No. 11/692,117.

As shown by FIG. 11, the housing 404, which houses the controller 47 ofFIG. 4, may be mounted on tank 502 and cover the controller 27. In thisregard, the rim 422 (not shown in FIG. 11) may pass into the compartmentsuch that frictional forces hold the housing 404 in place. In otherembodiments, other types of housings and other techniques for mounting ahousing to the tank 502 may be employed.

In one exemplary embodiment, as shown by FIG. 5, the controller 47comprises a wireless communication device 555 for enabling thecontroller 47 to communicate with a remote device. For example, thewireless communication device 55 may enable the control logic 45 tocommunicate with a remote user interface (not shown) for receiving userinputs and/or providing user outputs.

In one exemplary embodiment, the controller 27 is not equipped with awireless communication device. Thus, to establish a set point, a usermay provide an input via user input device 35 of controller 27. However,in such an example, a user may be required to be present at thecontroller 27. By adding the controller 47, wireless communication withthe remote user interface may be enabled so that a user does not need tobe present at the controller 27 to provide inputs, such as establishinga set point, or receive information about the operation of the system10.

In this regard, a user may provide an input for establishing a set pointto a remote user interface, which transmits data indicative of the inputto the controller 47 via wireless communication device 555. The controllogic 45 may then establish the set pint based on the data and/orcommunicate the data to the controller 27 so that the control logic 25may establish the set point. In another example, information about atemperature sensed by a temperature sensor may be transmitted to thecontroller 47. The control logic 45 may then wirelessly transmit suchinformation to a remote user interface via the wireless communicationdevice 555, and the remote user interface may display or otherwiseconvey the information to a user. In other examples, the wirelesscommunication device 555 may communicate other types of informationand/or enable other types of functions.

Note that is unnecessary for the controller 47 to directly control theoperation of the heating elements. For example, the controller 47 maysimply be sued to display data and/or receive inputs in one embodiment.In another embodiment, the controller 47 may only be used to communicatewireless data. Moreover, the controller 47 may be configured to performany number of functions in addition to or in lieu of the controller 27.

What is claimed is:
 1. A water heating system having a modular controlsystem, comprising: a tank; a heating element supported by the tank; afirst controller supported by the tank, the first controller coupled tothe heating element, the first controller including logic to activateand deactivate the heating element according to a first threshold value;and a second controller selectively coupled to the first controller andconfigured to communicate the first threshold value to the firstcontroller, and perform an additional function related to the operationof the water heater; and wherein the first controller is configured tocontrol the heating element mounted on the water heating system in anabsence of the second controller.
 2. The water heating system of claim1, wherein the second controller is configured to receive informationfrom a user for determining the first threshold value.
 3. The waterheating system of claim 1, wherein the second controller is configuredto determine the first threshold value based on a first algorithm. 4.The water heating system of claim 3, wherein the first algorithmincludes a usage history algorithm that determines the first thresholdvalue and a second threshold value based on the usage history of theheating element.
 5. The water heating system of claim 4, wherein thesecond controller is configured to communicate with the first controllerthe second threshold value, and wherein the first controller activatesand deactivates the heating element based on the first threshold valueand the second threshold value.
 6. The water heating system of claim 1,wherein the second controller includes a display.
 7. The water heatingsystem of claim 1, wherein the additional function performed by thesecond controller includes storing activation and deactivationinformation of the heating element.
 8. The water heating system of claim1, wherein the first controller is configured to communicate informationpertaining to the activation and deactivation of heating element to thesecond controller.
 9. The water heating system of claim 1, wherein thefirst controller and the second controller communicate wirelessly. 10.The water heating system of claim 1, wherein the first controller has afirst housing that covers components of the first controller, andwherein the second controller has a second housing, separate from thefirst housing, covering components of the second controller.
 11. Thewater heating system of claim 1, wherein the second controller isconfigured to send a wireless command to the first controllerinstructing the first controller when to activate the heating element.12. The water heating system of claim 1, wherein the second controlleris not directly coupled to the heating element.
 13. The water heatingsystem of claim 1, wherein the second controller is located remotelyfrom the tank.
 14. The water heating system of claim 1, wherein thesecond controller is selectively physically coupled to the firstcontroller.
 15. The water heating system of claim 1, wherein the firstcontroller includes an input device that is configured to receiveinformation regarding the first threshold value.
 16. A water heatingsystem having a modular control system, comprising: a tank; one or moreheating elements mounted on the water heating system; a first controllermounted on the tank and having a first communication port, the firstcommunication port having a first wireless transceiver, and the firstcontroller including logic for activating and deactivating all of theone or more heating elements mounted on the water heating system basedon a first threshold; and a second controller selectively coupled to thefirst controller via the first communication port, the second controllerconfigured to wirelessly send information regarding the first thresholdto the first controller, wherein the first controller is configured towirelessly communicate information regarding the activation anddeactivation of the one or more heating elements to the secondcontroller, and wherein the first controller is configured to controlthe activation and deactivation of all the one or more heating elementsin the absence of the second controller.
 17. The water heating system ofclaim 16, wherein the second controller has logic configured to receive,via a wireless communication device, data indicative of an input forestablishing a set point to be used for determining the first threshold.18. The water heating system of claim 17, wherein the logic of thesecond controller is configured to transmit, via the wirelesscommunication device, information pertaining to operation of the waterheating system to a remote device.
 19. The water heating system of claim16, wherein the first controller has a first housing that coverscomponents of the first controller, and wherein the second controllerhas a second housing, separate from the first housing, coveringcomponents of the second controller.
 20. The water heating system ofclaim 19, wherein the tank has a compartment, wherein the firstcontroller resides in the compartment, and wherein the second housinghas a rim inserted into the compartment and contacting a wall of thetank defining the compartment.